Ionic liquids (ILs) are a unique class of solvents with many potential applications, such as advanced separations, carbon capture, and absorption heating/cooling. Due to the large number of possible combinations of cations and anions, it is possible to tune the IL to obtain the required properties for the application of interest. Many ILs are very hydrophilic, while even the most hydrophobic ILs often absorb significant amounts of water. The presence of water in an IL can have a large effect on the system properties. For instance, a small amount of dissolved water often leads to a dramatic reduction in the viscosity of the mixture. Dissolved water also affects the ionic conductivity of ILs and alters the solvation power of ILs for both polar and non-polar solutes. Knowledge of the phase diagram of these IL/water mixtures therefore is essential when designing applications. Measuring isotherms often requires difficult and/or expensive experiments, and does not necessarily lead to a deeper understanding of the molecular-level interactions responsible for water-IL interactions. In contrast, molecular simulations are relatively inexpensive to perform, allowing one to screen potential ILs for a given application. Simulation also provides a detailed picture of how water and a given IL interact, thereby providing insight into ways of designing an IL to have a desired water solubility. Toward this end, Monte Carlo (MC) simulations have been performed to predict isotherms for a variety of IL/water mixtures. By varying the nature of the cation and anion, as well as exchanging some of the IL cations with a small metal cation, we can cause the IL to be more or less hydrophilic and shift the isotherm.

Phase equilibria and thermophysical properties of ionic liquid/water mixtures

247th National Meeting (2014)

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